Specified antenna performance characteristics are difficult to maintain after antennas are installed in different mobile devices. Even among mobile devices with identical or similar form factors, slightly different antenna-installation locations that may be attributable to manufacturing tolerances or errors typically result in deviations between the specified and the actual antenna performance. These deviations can negatively affect antenna performance and efficiency. For example, an antenna installed at a location offset by some distance (e.g., one or two millimeters) from its specified location may cause the antenna to deviate from its specified resonate frequency, which may result in a power amplifier wasting power while tuning the antenna to its originally specified resonant frequency. This inefficiency prematurely drains a battery of the mobile device, or results in suboptimal transmission and reception.
To address potential performance concerns, conventional antennas are specifically designed for various form factors. However, specifically designed antennas increase development costs and time-to-market for mobile devices. Moreover, once the antenna is installed, its efficiency cannot be readily improved because the conventional antenna is specifically designed and fully integrated with the transceiver in the mobile device. Furthermore, even for specifically designed antennas, unpredictable manufacturing errors, interference from the human body, or other environmental conditions may degrade performance. For example, a user's hand or head touching the mobile device will typically detune the antenna to a degree that is often unpredictable, as it depends on a user's physical characteristics, the way mobile devices are held, or other environmental factors. Performance degradation of multi-band or broadband antennas is difficult to dynamically improve because the environmental factors affecting the antenna may simultaneously detune multiple (or broad) frequency bands employed by the antenna.